The present disclosure relates to systems and methods for the control of fluid loss from a wellbore treatment fluid, such as a drilling fluid, to a subterranean formation.
Treatment fluids can be used in a variety of subterranean treatment operations. As used herein, the terms “treat,” “treatment,” “treating,” and grammatical equivalents thereof refer to any subterranean operation that uses a fluid in conjunction with achieving a desired function and/or for a desired purpose. Use of these terms does not imply any particular action by the treatment fluid. Illustrative treatment operations can include, for example, drilling operations, fracturing operations, cementing operations, and the like.
Natural resources such as oil or gas residing in a subterranean formation can be recovered by drilling wells that penetrate the formation. Drilling operations typically require the use of a drilling fluid. During drilling operations, a viscosified treatment fluid (e.g., a drilling fluid) passes down through the inside of the drill string, exits through the drill bit, and returns to the drilling rig through the annulus between the drill string and well bore. The various functions of a drilling fluid include removing drill cuttings from the wellbore, cooling and lubricating the drill bit, aiding in support of the drill pipe and drill bit, and providing a hydrostatic head to maintain the integrity of the wellbore walls and prevent well blowouts.
Specific drilling fluid systems are selected to optimize a drilling operation in accordance with the characteristics of a particular geological formation. Invert emulsion fluids, for example, are often used to drill swelling or sloughing shales, salt, gypsum, anhydrite and other evaporate formations, hydrogen sulfide-containing formations, and high-temperature formations (such as formations having a downhole temperature greater than about 300 degrees Fahrenheit (“° F.”) holes, among others. Invert emulsion fluids are characterized in that they comprise oil as the external or continuous phase of emulsion; such fluids often comprise between about 50:50 to about 95:5 by volume oil phase to water phase. Such oil-based drilling fluids often comprise, comprise, in addition to a base oil comprising the external phase of an invert emulsion, a saline, aqueous solution, such as a solution comprising about 30% calcium chloride, comprising the internal phase of the invert emulsion, one or more emulsifiers at the interface of the internal and external phases; and other agents or additives, such as surfactant, for suspension, weight or density, oil-wetting, fluid loss or filtration control, and rheology control.
Rheology is frequently an important property of the wellbore treatment fluid, and specific rheological parameters are preferred for drilling and circulating the fluid through the well bore. The fluid should be sufficiently viscous to suspend barite and drilled cuttings and to carry the cuttings to the well surface. However, the fluid should not be so viscous as to interfere with the drilling operation. Filtration control, which refers to the ability of a treatment fluid to prevent excessive loss of fluid into a formation, is also frequently an important property of a drilling fluid, particularly when drilling through permeable formations where the hydrostatic pressure exceeds the formation pressure. Certain surfactants are known to impart viscoelasticity to treatment fluids, but have heretofore generally been associated with poor fluid loss control or environmental concerns.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.